This mod is a very minimal approach to changing up the early tool sets, reskinning wooden tools as flint tools and stone tools as copper tools. You'll need their respective materials to craft them.

Some extra details:

• You can still punch trees to get wood.
• Copper is now able to be mined with a flint pickaxe.
• Flint rocks now spawn in certain biomes to make obtaining flint much easier.
• Unlike wooden tools, flint tools cannot be used as furnace fuel.

Technical bits:

• Blocks that can be harvested with flint tools can be tagged with needs_flint_tool. This behaves a bit differently than other tool tags, overriding any other tool requirements that particular block may have. If you want a block to not be harvestable with your fists, you will have to tag it with another tool tier requirement as well.
  • In addtion, items that can harvest these blocks can be tagged with flint_tools, which contains the entire flint tool set by default.
• Biomes that have flint rocks in them are tagged with has_rocks. You can modify this to change which biomes spawn rocks, though this should be compatible with many mods already.